Due to our knowledge of jelly babies we have decided to combine red with black and green with yellow because we feel they would be predated on very similarly. Also our expected values for red and yellow are very low therefore need to be combined.
The null hypothesis is that there will be no significant difference in the population frequencies between the different habitats.
We decided to compare the proportion of polymorphisms across our samples.
At a p value of 0.05, our null hypothesis will be true if we obtain a chi squared value which is greater than 0.05. However if the p value is equal to or less than to 0.05, it will suggest that our results will be significant.
Population
Black + Red
Green + Yellow
Orange
Total
1
Grass
6
10
4
20
2
Bush
6
8
6
20
3
Grass
8
10
2
20
4
Bush
7
10
3
20
5
Grass
8
8
4
20
6
Bush
6
10
4
20
Total
41
56
23
120
Black + Red
Green + Yellow
Orange
Expected Value (E)
6.833
9.333
3.833
Now our expected values are significant enough for Chi square test
Chi Square Test
All six populations:
Population
Black + Red
Green + Yellow
Orange
Total
X2 1
Grass
0.102
0.048
0.007
0.157
X2 2
Bush
0.102
0.190
1.225
1.517
X2 3
Grass
0.199
0.048
0.877
1.124
X2 4
Bush
0.004
0.048
0.181
0.233
X2 5
Grass
0.199
0.190
0.007
0.396
X2 6
Bush
0.102
0.048
0.007
0.157
Total
0.708
0.572
2.304
3.584
Grass:
Population
Black + Red
Green + Yellow
Orange
Total
1
Grass
6
10
4
20
3
Grass
8
10
2
20
5
Grass
8
8
4
20
Total
22
28
10
Black + Red
Green + Yellow
Orange
Expected Value (E)
7.333
9.333
3.333
Population
Black + Red
Green + Yellow
Orange
Total
X2 1
Grass
0.242
0.048
0.133
0.423
X2 3
Grass
0.061
0.048
0.533
0.642
X2 5
Grass
0.061
0.190
0.133
0.384
Total
0.364
0.286
0.799
1.449
DF
4
Critical Value (0.05)
9.488
Chi Squared value
1.449
The chi squared value of 1.449, is significantly lower than the critical value of 9.488 therefore we can accept the null hypothesis which is that the difference in allele frequencies is not significant between populations. therefore the polymorphism of snails may be attributed to selection.
Bush:
Population
Black + Red
Green + Yellow
Orange
Total
2
Bush
6
8
6
20
4
Bush
7
10
3
20
6
Bush
6
10
4
20
Total
19
28
13
Black + Red
Green + Yellow
Orange
Expected Value (E)
6.333
9.333
4.333
Population
Black + Red
Green + Yellow
Orange
Total
2
Bush
0.018
0.190
0.641
0.849
4
Bush
0.070
0.048
0.410
0.528
6
Bush
0.018
0.048
0.026
0.092
Total
0.106
0.286
1.077
1.469
DF
4
Critical Value (0.05)
9.488
Chi Squared value
1.469
Our chi squared value of 1.469 is significantly lower than our critical value of 9.488 and therefore we can conclude that our null hypothesis can be accepted. Our null hypothesis suggests that the allele frequencies are not significant between populations.
1
Black Green Orange Red Yellow
5 9 4 1 1
2
Black Green Orange Red
3 8 6 3
3
Black Green Orange Yellow
8 9 2 1
4
Black Green Orange Red Yellow
4 5 3 3 5
5
Black Green Orange Yellow
8 6 4 2
6
Black Green Orange Yellow
6 8 4 2
Chi Square Test
All six populations:
Grass:
Bush: